I am being told that the specific provisions in my document may be ignored and give one division an ancilliary benefit that is only provided to another division. The documents are written by division and provide different formulas and retirement provisions. One division intended to match another's benefit, but failed to modify their document. Now we have people saying it's o.k. to use that other divisions benefits under "the one plan rule". Is this even a real concept? Is there a code citation that backs up using another benefit structure simply because the two divisions have the same parent company?

Not that I know of. I have always thought you had to follow the document, even if you don't agree with it. I have seen where documents are corrected to match past practice, but that generally only works if you are giving more and even then the attorneys get a bit concerned.

Ask their ERISA counsel for a letter instructing you to ignore the plan document. If you get it, I think you are ok. If not, the issue will get resolved.

The problem seems to have resolved itself. When "they" were asked for a code section to back up this mysterious rule, none could be provided.